1config ARCH
2 string
3 option env="ARCH"
4 5config KERNELVERSION
6 string
7 option env="KERNELVERSION"
8 9config DEFCONFIG_LIST
10 string
11 depends on !UML
12 option defconfig_list
13 default "/lib/modules/$UNAME_RELEASE/.config"
14 default "/etc/kernel-config"
15 default "/boot/config-$UNAME_RELEASE"
16 default "$ARCH_DEFCONFIG"
17 default "arch/$ARCH/defconfig"
18 19config CONSTRUCTORS
20 bool
21 depends on !UML
22 23config HAVE_IRQ_WORK
24 bool
25 26config IRQ_WORK
27 bool
28 depends on HAVE_IRQ_WORK
29 30config BUILDTIME_EXTABLE_SORT
31 bool
32 33menu "General setup"
34 35config EXPERIMENTAL
36 bool "Prompt for development and/or incomplete code/drivers"
37 ---help---
38 Some of the various things that Linux supports (such as network
39 drivers, file systems, network protocols, etc.) can be in a state
40 of development where the functionality, stability, or the level of
41 testing is not yet high enough for general use. This is usually
42 known as the "alpha-test" phase among developers. If a feature is
43 currently in alpha-test, then the developers usually discourage
44 uninformed widespread use of this feature by the general public to
45 avoid "Why doesn't this work?" type mail messages. However, active
46 testing and use of these systems is welcomed. Just be aware that it
47 may not meet the normal level of reliability or it may fail to work
48 in some special cases. Detailed bug reports from people familiar
49 with the kernel internals are usually welcomed by the developers
50 (before submitting bug reports, please read the documents
51 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
52 <file:Documentation/BUG-HUNTING>, and
53 <file:Documentation/oops-tracing.txt> in the kernel source).
54 55 This option will also make obsoleted drivers available. These are
56 drivers that have been replaced by something else, and/or are
57 scheduled to be removed in a future kernel release.
58 59 Unless you intend to help test and develop a feature or driver that
60 falls into this category, or you have a situation that requires
61 using these features, you should probably say N here, which will
62 cause the configurator to present you with fewer choices. If
63 you say Y here, you will be offered the choice of using features or
64 drivers that are currently considered to be in the alpha-test phase.
65 66config BROKEN
67 bool
68 69config BROKEN_ON_SMP
70 bool
71 depends on BROKEN || !SMP
72 default y
73 74config INIT_ENV_ARG_LIMIT
75 int
76 default 32 if !UML
77 default 128 if UML
78 help
79 Maximum of each of the number of arguments and environment
80 variables passed to init from the kernel command line.
81 82 83config CROSS_COMPILE
84 string "Cross-compiler tool prefix"
85 help
86 Same as running 'make CROSS_COMPILE=prefix-' but stored for
87 default make runs in this kernel build directory. You don't
88 need to set this unless you want the configured kernel build
89 directory to select the cross-compiler automatically.
90 91config LOCALVERSION
92 string "Local version - append to kernel release"
93 help
94 Append an extra string to the end of your kernel version.
95 This will show up when you type uname, for example.
96 The string you set here will be appended after the contents of
97 any files with a filename matching localversion* in your
98 object and source tree, in that order. Your total string can
99 be a maximum of 64 characters.
100 101config LOCALVERSION_AUTO
102 bool "Automatically append version information to the version string"
103 default y
104 help
105 This will try to automatically determine if the current tree is a
106 release tree by looking for git tags that belong to the current
107 top of tree revision.
108 109 A string of the format -gxxxxxxxx will be added to the localversion
110 if a git-based tree is found. The string generated by this will be
111 appended after any matching localversion* files, and after the value
112 set in CONFIG_LOCALVERSION.
113 114 (The actual string used here is the first eight characters produced
115 by running the command:
116 117 $ git rev-parse --verify HEAD
118 119 which is done within the script "scripts/setlocalversion".)
120 121config HAVE_KERNEL_GZIP
122 bool
123 124config HAVE_KERNEL_BZIP2
125 bool
126 127config HAVE_KERNEL_LZMA
128 bool
129 130config HAVE_KERNEL_XZ
131 bool
132 133config HAVE_KERNEL_LZO
134 bool
135 136choice
137 prompt "Kernel compression mode"
138 default KERNEL_GZIP
139 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
140 help
141 The linux kernel is a kind of self-extracting executable.
142 Several compression algorithms are available, which differ
143 in efficiency, compression and decompression speed.
144 Compression speed is only relevant when building a kernel.
145 Decompression speed is relevant at each boot.
146 147 If you have any problems with bzip2 or lzma compressed
148 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
149 version of this functionality (bzip2 only), for 2.4, was
150 supplied by Christian Ludwig)
151 152 High compression options are mostly useful for users, who
153 are low on disk space (embedded systems), but for whom ram
154 size matters less.
155 156 If in doubt, select 'gzip'
157 158config KERNEL_GZIP
159 bool "Gzip"
160 depends on HAVE_KERNEL_GZIP
161 help
162 The old and tried gzip compression. It provides a good balance
163 between compression ratio and decompression speed.
164 165config KERNEL_BZIP2
166 bool "Bzip2"
167 depends on HAVE_KERNEL_BZIP2
168 help
169 Its compression ratio and speed is intermediate.
170 Decompression speed is slowest among the choices. The kernel
171 size is about 10% smaller with bzip2, in comparison to gzip.
172 Bzip2 uses a large amount of memory. For modern kernels you
173 will need at least 8MB RAM or more for booting.
174 175config KERNEL_LZMA
176 bool "LZMA"
177 depends on HAVE_KERNEL_LZMA
178 help
179 This compression algorithm's ratio is best. Decompression speed
180 is between gzip and bzip2. Compression is slowest.
181 The kernel size is about 33% smaller with LZMA in comparison to gzip.
182 183config KERNEL_XZ
184 bool "XZ"
185 depends on HAVE_KERNEL_XZ
186 help
187 XZ uses the LZMA2 algorithm and instruction set specific
188 BCJ filters which can improve compression ratio of executable
189 code. The size of the kernel is about 30% smaller with XZ in
190 comparison to gzip. On architectures for which there is a BCJ
191 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
192 will create a few percent smaller kernel than plain LZMA.
193 194 The speed is about the same as with LZMA: The decompression
195 speed of XZ is better than that of bzip2 but worse than gzip
196 and LZO. Compression is slow.
197 198config KERNEL_LZO
199 bool "LZO"
200 depends on HAVE_KERNEL_LZO
201 help
202 Its compression ratio is the poorest among the choices. The kernel
203 size is about 10% bigger than gzip; however its speed
204 (both compression and decompression) is the fastest.
205 206endchoice
207 208config DEFAULT_HOSTNAME
209 string "Default hostname"
210 default "(none)"
211 help
212 This option determines the default system hostname before userspace
213 calls sethostname(2). The kernel traditionally uses "(none)" here,
214 but you may wish to use a different default here to make a minimal
215 system more usable with less configuration.
216 217config SWAP
218 bool "Support for paging of anonymous memory (swap)"
219 depends on MMU && BLOCK
220 default y
221 help
222 This option allows you to choose whether you want to have support
223 for so called swap devices or swap files in your kernel that are
224 used to provide more virtual memory than the actual RAM present
225 in your computer. If unsure say Y.
226 227config SYSVIPC
228 bool "System V IPC"
229 ---help---
230 Inter Process Communication is a suite of library functions and
231 system calls which let processes (running programs) synchronize and
232 exchange information. It is generally considered to be a good thing,
233 and some programs won't run unless you say Y here. In particular, if
234 you want to run the DOS emulator dosemu under Linux (read the
235 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
236 you'll need to say Y here.
237 238 You can find documentation about IPC with "info ipc" and also in
239 section 6.4 of the Linux Programmer's Guide, available from
240 <http://www.tldp.org/guides.html>.
241 242config SYSVIPC_SYSCTL
243 bool
244 depends on SYSVIPC
245 depends on SYSCTL
246 default y
247 248config POSIX_MQUEUE
249 bool "POSIX Message Queues"
250 depends on NET && EXPERIMENTAL
251 ---help---
252 POSIX variant of message queues is a part of IPC. In POSIX message
253 queues every message has a priority which decides about succession
254 of receiving it by a process. If you want to compile and run
255 programs written e.g. for Solaris with use of its POSIX message
256 queues (functions mq_*) say Y here.
257 258 POSIX message queues are visible as a filesystem called 'mqueue'
259 and can be mounted somewhere if you want to do filesystem
260 operations on message queues.
261 262 If unsure, say Y.
263 264config POSIX_MQUEUE_SYSCTL
265 bool
266 depends on POSIX_MQUEUE
267 depends on SYSCTL
268 default y
269 270config FHANDLE
271 bool "open by fhandle syscalls"
272 select EXPORTFS
273 help
274 If you say Y here, a user level program will be able to map
275 file names to handle and then later use the handle for
276 different file system operations. This is useful in implementing
277 userspace file servers, which now track files using handles instead
278 of names. The handle would remain the same even if file names
279 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
280 syscalls.
281 282config AUDIT
283 bool "Auditing support"
284 depends on NET
285 help
286 Enable auditing infrastructure that can be used with another
287 kernel subsystem, such as SELinux (which requires this for
288 logging of avc messages output). Does not do system-call
289 auditing without CONFIG_AUDITSYSCALL.
290 291config AUDITSYSCALL
292 bool "Enable system-call auditing support"
293 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT))
294 default y if SECURITY_SELINUX
295 help
296 Enable low-overhead system-call auditing infrastructure that
297 can be used independently or with another kernel subsystem,
298 such as SELinux.
299 300config AUDIT_WATCH
301 def_bool y
302 depends on AUDITSYSCALL
303 select FSNOTIFY
304 305config AUDIT_TREE
306 def_bool y
307 depends on AUDITSYSCALL
308 select FSNOTIFY
309 310config AUDIT_LOGINUID_IMMUTABLE
311 bool "Make audit loginuid immutable"
312 depends on AUDIT
313 help
314 The config option toggles if a task setting its loginuid requires
315 CAP_SYS_AUDITCONTROL or if that task should require no special permissions
316 but should instead only allow setting its loginuid if it was never
317 previously set. On systems which use systemd or a similar central
318 process to restart login services this should be set to true. On older
319 systems in which an admin would typically have to directly stop and
320 start processes this should be set to false. Setting this to true allows
321 one to drop potentially dangerous capabilites from the login tasks,
322 but may not be backwards compatible with older init systems.
323 324source "kernel/irq/Kconfig"
325source "kernel/time/Kconfig"
326 327menu "CPU/Task time and stats accounting"
328 329choice
330 prompt "Cputime accounting"
331 default TICK_CPU_ACCOUNTING if !PPC64
332 default VIRT_CPU_ACCOUNTING if PPC64
333 334# Kind of a stub config for the pure tick based cputime accounting
335config TICK_CPU_ACCOUNTING
336 bool "Simple tick based cputime accounting"
337 depends on !S390
338 help
339 This is the basic tick based cputime accounting that maintains
340 statistics about user, system and idle time spent on per jiffies
341 granularity.
342 343 If unsure, say Y.
344 345config VIRT_CPU_ACCOUNTING
346 bool "Deterministic task and CPU time accounting"
347 depends on HAVE_VIRT_CPU_ACCOUNTING
348 help
349 Select this option to enable more accurate task and CPU time
350 accounting. This is done by reading a CPU counter on each
351 kernel entry and exit and on transitions within the kernel
352 between system, softirq and hardirq state, so there is a
353 small performance impact. In the case of s390 or IBM POWER > 5,
354 this also enables accounting of stolen time on logically-partitioned
355 systems.
356 357config IRQ_TIME_ACCOUNTING
358 bool "Fine granularity task level IRQ time accounting"
359 depends on HAVE_IRQ_TIME_ACCOUNTING
360 help
361 Select this option to enable fine granularity task irq time
362 accounting. This is done by reading a timestamp on each
363 transitions between softirq and hardirq state, so there can be a
364 small performance impact.
365 366 If in doubt, say N here.
367 368endchoice
369 370config BSD_PROCESS_ACCT
371 bool "BSD Process Accounting"
372 help
373 If you say Y here, a user level program will be able to instruct the
374 kernel (via a special system call) to write process accounting
375 information to a file: whenever a process exits, information about
376 that process will be appended to the file by the kernel. The
377 information includes things such as creation time, owning user,
378 command name, memory usage, controlling terminal etc. (the complete
379 list is in the struct acct in <file:include/linux/acct.h>). It is
380 up to the user level program to do useful things with this
381 information. This is generally a good idea, so say Y.
382 383config BSD_PROCESS_ACCT_V3
384 bool "BSD Process Accounting version 3 file format"
385 depends on BSD_PROCESS_ACCT
386 default n
387 help
388 If you say Y here, the process accounting information is written
389 in a new file format that also logs the process IDs of each
390 process and it's parent. Note that this file format is incompatible
391 with previous v0/v1/v2 file formats, so you will need updated tools
392 for processing it. A preliminary version of these tools is available
393 at <http://www.gnu.org/software/acct/>.
394 395config TASKSTATS
396 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
397 depends on NET
398 default n
399 help
400 Export selected statistics for tasks/processes through the
401 generic netlink interface. Unlike BSD process accounting, the
402 statistics are available during the lifetime of tasks/processes as
403 responses to commands. Like BSD accounting, they are sent to user
404 space on task exit.
405 406 Say N if unsure.
407 408config TASK_DELAY_ACCT
409 bool "Enable per-task delay accounting (EXPERIMENTAL)"
410 depends on TASKSTATS
411 help
412 Collect information on time spent by a task waiting for system
413 resources like cpu, synchronous block I/O completion and swapping
414 in pages. Such statistics can help in setting a task's priorities
415 relative to other tasks for cpu, io, rss limits etc.
416 417 Say N if unsure.
418 419config TASK_XACCT
420 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
421 depends on TASKSTATS
422 help
423 Collect extended task accounting data and send the data
424 to userland for processing over the taskstats interface.
425 426 Say N if unsure.
427 428config TASK_IO_ACCOUNTING
429 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
430 depends on TASK_XACCT
431 help
432 Collect information on the number of bytes of storage I/O which this
433 task has caused.
434 435 Say N if unsure.
436 437endmenu # "CPU/Task time and stats accounting"
438 439menu "RCU Subsystem"
440 441choice
442 prompt "RCU Implementation"
443 default TREE_RCU
444 445config TREE_RCU
446 bool "Tree-based hierarchical RCU"
447 depends on !PREEMPT && SMP
448 help
449 This option selects the RCU implementation that is
450 designed for very large SMP system with hundreds or
451 thousands of CPUs. It also scales down nicely to
452 smaller systems.
453 454config TREE_PREEMPT_RCU
455 bool "Preemptible tree-based hierarchical RCU"
456 depends on PREEMPT && SMP
457 help
458 This option selects the RCU implementation that is
459 designed for very large SMP systems with hundreds or
460 thousands of CPUs, but for which real-time response
461 is also required. It also scales down nicely to
462 smaller systems.
463 464config TINY_RCU
465 bool "UP-only small-memory-footprint RCU"
466 depends on !PREEMPT && !SMP
467 help
468 This option selects the RCU implementation that is
469 designed for UP systems from which real-time response
470 is not required. This option greatly reduces the
471 memory footprint of RCU.
472 473config TINY_PREEMPT_RCU
474 bool "Preemptible UP-only small-memory-footprint RCU"
475 depends on PREEMPT && !SMP
476 help
477 This option selects the RCU implementation that is designed
478 for real-time UP systems. This option greatly reduces the
479 memory footprint of RCU.
480 481endchoice
482 483config PREEMPT_RCU
484 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
485 help
486 This option enables preemptible-RCU code that is common between
487 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
488 489config CONTEXT_TRACKING
490 bool
491 492config RCU_USER_QS
493 bool "Consider userspace as in RCU extended quiescent state"
494 depends on HAVE_CONTEXT_TRACKING && SMP
495 select CONTEXT_TRACKING
496 help
497 This option sets hooks on kernel / userspace boundaries and
498 puts RCU in extended quiescent state when the CPU runs in
499 userspace. It means that when a CPU runs in userspace, it is
500 excluded from the global RCU state machine and thus doesn't
501 try to keep the timer tick on for RCU.
502 503 Unless you want to hack and help the development of the full
504 dynticks mode, you shouldn't enable this option. It also
505 adds unnecessary overhead.
506 507 If unsure say N
508 509config CONTEXT_TRACKING_FORCE
510 bool "Force context tracking"
511 depends on CONTEXT_TRACKING
512 help
513 Probe on user/kernel boundaries by default in order to
514 test the features that rely on it such as userspace RCU extended
515 quiescent states.
516 This test is there for debugging until we have a real user like the
517 full dynticks mode.
518 519config RCU_FANOUT
520 int "Tree-based hierarchical RCU fanout value"
521 range 2 64 if 64BIT
522 range 2 32 if !64BIT
523 depends on TREE_RCU || TREE_PREEMPT_RCU
524 default 64 if 64BIT
525 default 32 if !64BIT
526 help
527 This option controls the fanout of hierarchical implementations
528 of RCU, allowing RCU to work efficiently on machines with
529 large numbers of CPUs. This value must be at least the fourth
530 root of NR_CPUS, which allows NR_CPUS to be insanely large.
531 The default value of RCU_FANOUT should be used for production
532 systems, but if you are stress-testing the RCU implementation
533 itself, small RCU_FANOUT values allow you to test large-system
534 code paths on small(er) systems.
535 536 Select a specific number if testing RCU itself.
537 Take the default if unsure.
538 539config RCU_FANOUT_LEAF
540 int "Tree-based hierarchical RCU leaf-level fanout value"
541 range 2 RCU_FANOUT if 64BIT
542 range 2 RCU_FANOUT if !64BIT
543 depends on TREE_RCU || TREE_PREEMPT_RCU
544 default 16
545 help
546 This option controls the leaf-level fanout of hierarchical
547 implementations of RCU, and allows trading off cache misses
548 against lock contention. Systems that synchronize their
549 scheduling-clock interrupts for energy-efficiency reasons will
550 want the default because the smaller leaf-level fanout keeps
551 lock contention levels acceptably low. Very large systems
552 (hundreds or thousands of CPUs) will instead want to set this
553 value to the maximum value possible in order to reduce the
554 number of cache misses incurred during RCU's grace-period
555 initialization. These systems tend to run CPU-bound, and thus
556 are not helped by synchronized interrupts, and thus tend to
557 skew them, which reduces lock contention enough that large
558 leaf-level fanouts work well.
559 560 Select a specific number if testing RCU itself.
561 562 Select the maximum permissible value for large systems.
563 564 Take the default if unsure.
565 566config RCU_FANOUT_EXACT
567 bool "Disable tree-based hierarchical RCU auto-balancing"
568 depends on TREE_RCU || TREE_PREEMPT_RCU
569 default n
570 help
571 This option forces use of the exact RCU_FANOUT value specified,
572 regardless of imbalances in the hierarchy. This is useful for
573 testing RCU itself, and might one day be useful on systems with
574 strong NUMA behavior.
575 576 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
577 578 Say N if unsure.
579 580config RCU_FAST_NO_HZ
581 bool "Accelerate last non-dyntick-idle CPU's grace periods"
582 depends on NO_HZ && SMP
583 default n
584 help
585 This option causes RCU to attempt to accelerate grace periods in
586 order to allow CPUs to enter dynticks-idle state more quickly.
587 On the other hand, this option increases the overhead of the
588 dynticks-idle checking, thus degrading scheduling latency.
589 590 Say Y if energy efficiency is critically important, and you don't
591 care about real-time response.
592 593 Say N if you are unsure.
594 595config TREE_RCU_TRACE
596 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
597 select DEBUG_FS
598 help
599 This option provides tracing for the TREE_RCU and
600 TREE_PREEMPT_RCU implementations, permitting Makefile to
601 trivially select kernel/rcutree_trace.c.
602 603config RCU_BOOST
604 bool "Enable RCU priority boosting"
605 depends on RT_MUTEXES && PREEMPT_RCU
606 default n
607 help
608 This option boosts the priority of preempted RCU readers that
609 block the current preemptible RCU grace period for too long.
610 This option also prevents heavy loads from blocking RCU
611 callback invocation for all flavors of RCU.
612 613 Say Y here if you are working with real-time apps or heavy loads
614 Say N here if you are unsure.
615 616config RCU_BOOST_PRIO
617 int "Real-time priority to boost RCU readers to"
618 range 1 99
619 depends on RCU_BOOST
620 default 1
621 help
622 This option specifies the real-time priority to which long-term
623 preempted RCU readers are to be boosted. If you are working
624 with a real-time application that has one or more CPU-bound
625 threads running at a real-time priority level, you should set
626 RCU_BOOST_PRIO to a priority higher then the highest-priority
627 real-time CPU-bound thread. The default RCU_BOOST_PRIO value
628 of 1 is appropriate in the common case, which is real-time
629 applications that do not have any CPU-bound threads.
630 631 Some real-time applications might not have a single real-time
632 thread that saturates a given CPU, but instead might have
633 multiple real-time threads that, taken together, fully utilize
634 that CPU. In this case, you should set RCU_BOOST_PRIO to
635 a priority higher than the lowest-priority thread that is
636 conspiring to prevent the CPU from running any non-real-time
637 tasks. For example, if one thread at priority 10 and another
638 thread at priority 5 are between themselves fully consuming
639 the CPU time on a given CPU, then RCU_BOOST_PRIO should be
640 set to priority 6 or higher.
641 642 Specify the real-time priority, or take the default if unsure.
643 644config RCU_BOOST_DELAY
645 int "Milliseconds to delay boosting after RCU grace-period start"
646 range 0 3000
647 depends on RCU_BOOST
648 default 500
649 help
650 This option specifies the time to wait after the beginning of
651 a given grace period before priority-boosting preempted RCU
652 readers blocking that grace period. Note that any RCU reader
653 blocking an expedited RCU grace period is boosted immediately.
654 655 Accept the default if unsure.
656 657config RCU_NOCB_CPU
658 bool "Offload RCU callback processing from boot-selected CPUs"
659 depends on TREE_RCU || TREE_PREEMPT_RCU
660 default n
661 help
662 Use this option to reduce OS jitter for aggressive HPC or
663 real-time workloads. It can also be used to offload RCU
664 callback invocation to energy-efficient CPUs in battery-powered
665 asymmetric multiprocessors.
666 667 This option offloads callback invocation from the set of
668 CPUs specified at boot time by the rcu_nocbs parameter.
669 For each such CPU, a kthread ("rcuoN") will be created to
670 invoke callbacks, where the "N" is the CPU being offloaded.
671 Nothing prevents this kthread from running on the specified
672 CPUs, but (1) the kthreads may be preempted between each
673 callback, and (2) affinity or cgroups can be used to force
674 the kthreads to run on whatever set of CPUs is desired.
675 676 Say Y here if you want reduced OS jitter on selected CPUs.
677 Say N here if you are unsure.
678 679endmenu # "RCU Subsystem"
680 681config IKCONFIG
682 tristate "Kernel .config support"
683 ---help---
684 This option enables the complete Linux kernel ".config" file
685 contents to be saved in the kernel. It provides documentation
686 of which kernel options are used in a running kernel or in an
687 on-disk kernel. This information can be extracted from the kernel
688 image file with the script scripts/extract-ikconfig and used as
689 input to rebuild the current kernel or to build another kernel.
690 It can also be extracted from a running kernel by reading
691 /proc/config.gz if enabled (below).
692 693config IKCONFIG_PROC
694 bool "Enable access to .config through /proc/config.gz"
695 depends on IKCONFIG && PROC_FS
696 ---help---
697 This option enables access to the kernel configuration file
698 through /proc/config.gz.
699 700config LOG_BUF_SHIFT
701 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
702 range 12 21
703 default 17
704 help
705 Select kernel log buffer size as a power of 2.
706 Examples:
707 17 => 128 KB
708 16 => 64 KB
709 15 => 32 KB
710 14 => 16 KB
711 13 => 8 KB
712 12 => 4 KB
713 714#
715# Architectures with an unreliable sched_clock() should select this:
716#
717config HAVE_UNSTABLE_SCHED_CLOCK
718 bool
719 720#
721# For architectures that want to enable the support for NUMA-affine scheduler
722# balancing logic:
723#
724config ARCH_SUPPORTS_NUMA_BALANCING
725 bool
726 727# For architectures that (ab)use NUMA to represent different memory regions
728# all cpu-local but of different latencies, such as SuperH.
729#
730config ARCH_WANT_NUMA_VARIABLE_LOCALITY
731 bool
732 733#
734# For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
735config ARCH_WANTS_PROT_NUMA_PROT_NONE
736 bool
737 738config ARCH_USES_NUMA_PROT_NONE
739 bool
740 default y
741 depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
742 depends on NUMA_BALANCING
743 744config NUMA_BALANCING_DEFAULT_ENABLED
745 bool "Automatically enable NUMA aware memory/task placement"
746 default y
747 depends on NUMA_BALANCING
748 help
749 If set, autonumic NUMA balancing will be enabled if running on a NUMA
750 machine.
751 752config NUMA_BALANCING
753 bool "Memory placement aware NUMA scheduler"
754 depends on ARCH_SUPPORTS_NUMA_BALANCING
755 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
756 depends on SMP && NUMA && MIGRATION
757 help
758 This option adds support for automatic NUMA aware memory/task placement.
759 The mechanism is quite primitive and is based on migrating memory when
760 it is references to the node the task is running on.
761 762 This system will be inactive on UMA systems.
763 764menuconfig CGROUPS
765 boolean "Control Group support"
766 depends on EVENTFD
767 help
768 This option adds support for grouping sets of processes together, for
769 use with process control subsystems such as Cpusets, CFS, memory
770 controls or device isolation.
771 See
772 - Documentation/scheduler/sched-design-CFS.txt (CFS)
773 - Documentation/cgroups/ (features for grouping, isolation
774 and resource control)
775 776 Say N if unsure.
777 778if CGROUPS
779 780config CGROUP_DEBUG
781 bool "Example debug cgroup subsystem"
782 default n
783 help
784 This option enables a simple cgroup subsystem that
785 exports useful debugging information about the cgroups
786 framework.
787 788 Say N if unsure.
789 790config CGROUP_FREEZER
791 bool "Freezer cgroup subsystem"
792 help
793 Provides a way to freeze and unfreeze all tasks in a
794 cgroup.
795 796config CGROUP_DEVICE
797 bool "Device controller for cgroups"
798 help
799 Provides a cgroup implementing whitelists for devices which
800 a process in the cgroup can mknod or open.
801 802config CPUSETS
803 bool "Cpuset support"
804 help
805 This option will let you create and manage CPUSETs which
806 allow dynamically partitioning a system into sets of CPUs and
807 Memory Nodes and assigning tasks to run only within those sets.
808 This is primarily useful on large SMP or NUMA systems.
809 810 Say N if unsure.
811 812config PROC_PID_CPUSET
813 bool "Include legacy /proc/<pid>/cpuset file"
814 depends on CPUSETS
815 default y
816 817config CGROUP_CPUACCT
818 bool "Simple CPU accounting cgroup subsystem"
819 help
820 Provides a simple Resource Controller for monitoring the
821 total CPU consumed by the tasks in a cgroup.
822 823config RESOURCE_COUNTERS
824 bool "Resource counters"
825 help
826 This option enables controller independent resource accounting
827 infrastructure that works with cgroups.
828 829config MEMCG
830 bool "Memory Resource Controller for Control Groups"
831 depends on RESOURCE_COUNTERS
832 select MM_OWNER
833 help
834 Provides a memory resource controller that manages both anonymous
835 memory and page cache. (See Documentation/cgroups/memory.txt)
836 837 Note that setting this option increases fixed memory overhead
838 associated with each page of memory in the system. By this,
839 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
840 usage tracking struct at boot. Total amount of this is printed out
841 at boot.
842 843 Only enable when you're ok with these trade offs and really
844 sure you need the memory resource controller. Even when you enable
845 this, you can set "cgroup_disable=memory" at your boot option to
846 disable memory resource controller and you can avoid overheads.
847 (and lose benefits of memory resource controller)
848 849 This config option also selects MM_OWNER config option, which
850 could in turn add some fork/exit overhead.
851 852config MEMCG_SWAP
853 bool "Memory Resource Controller Swap Extension"
854 depends on MEMCG && SWAP
855 help
856 Add swap management feature to memory resource controller. When you
857 enable this, you can limit mem+swap usage per cgroup. In other words,
858 when you disable this, memory resource controller has no cares to
859 usage of swap...a process can exhaust all of the swap. This extension
860 is useful when you want to avoid exhaustion swap but this itself
861 adds more overheads and consumes memory for remembering information.
862 Especially if you use 32bit system or small memory system, please
863 be careful about enabling this. When memory resource controller
864 is disabled by boot option, this will be automatically disabled and
865 there will be no overhead from this. Even when you set this config=y,
866 if boot option "swapaccount=0" is set, swap will not be accounted.
867 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
868 size is 4096bytes, 512k per 1Gbytes of swap.
869config MEMCG_SWAP_ENABLED
870 bool "Memory Resource Controller Swap Extension enabled by default"
871 depends on MEMCG_SWAP
872 default y
873 help
874 Memory Resource Controller Swap Extension comes with its price in
875 a bigger memory consumption. General purpose distribution kernels
876 which want to enable the feature but keep it disabled by default
877 and let the user enable it by swapaccount boot command line
878 parameter should have this option unselected.
879 For those who want to have the feature enabled by default should
880 select this option (if, for some reason, they need to disable it
881 then swapaccount=0 does the trick).
882config MEMCG_KMEM
883 bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)"
884 depends on MEMCG && EXPERIMENTAL
885 depends on SLUB || SLAB
886 help
887 The Kernel Memory extension for Memory Resource Controller can limit
888 the amount of memory used by kernel objects in the system. Those are
889 fundamentally different from the entities handled by the standard
890 Memory Controller, which are page-based, and can be swapped. Users of
891 the kmem extension can use it to guarantee that no group of processes
892 will ever exhaust kernel resources alone.
893 894config CGROUP_HUGETLB
895 bool "HugeTLB Resource Controller for Control Groups"
896 depends on RESOURCE_COUNTERS && HUGETLB_PAGE && EXPERIMENTAL
897 default n
898 help
899 Provides a cgroup Resource Controller for HugeTLB pages.
900 When you enable this, you can put a per cgroup limit on HugeTLB usage.
901 The limit is enforced during page fault. Since HugeTLB doesn't
902 support page reclaim, enforcing the limit at page fault time implies
903 that, the application will get SIGBUS signal if it tries to access
904 HugeTLB pages beyond its limit. This requires the application to know
905 beforehand how much HugeTLB pages it would require for its use. The
906 control group is tracked in the third page lru pointer. This means
907 that we cannot use the controller with huge page less than 3 pages.
908 909config CGROUP_PERF
910 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
911 depends on PERF_EVENTS && CGROUPS
912 help
913 This option extends the per-cpu mode to restrict monitoring to
914 threads which belong to the cgroup specified and run on the
915 designated cpu.
916 917 Say N if unsure.
918 919menuconfig CGROUP_SCHED
920 bool "Group CPU scheduler"
921 default n
922 help
923 This feature lets CPU scheduler recognize task groups and control CPU
924 bandwidth allocation to such task groups. It uses cgroups to group
925 tasks.
926 927if CGROUP_SCHED
928config FAIR_GROUP_SCHED
929 bool "Group scheduling for SCHED_OTHER"
930 depends on CGROUP_SCHED
931 default CGROUP_SCHED
932 933config CFS_BANDWIDTH
934 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
935 depends on EXPERIMENTAL
936 depends on FAIR_GROUP_SCHED
937 default n
938 help
939 This option allows users to define CPU bandwidth rates (limits) for
940 tasks running within the fair group scheduler. Groups with no limit
941 set are considered to be unconstrained and will run with no
942 restriction.
943 See tip/Documentation/scheduler/sched-bwc.txt for more information.
944 945config RT_GROUP_SCHED
946 bool "Group scheduling for SCHED_RR/FIFO"
947 depends on EXPERIMENTAL
948 depends on CGROUP_SCHED
949 default n
950 help
951 This feature lets you explicitly allocate real CPU bandwidth
952 to task groups. If enabled, it will also make it impossible to
953 schedule realtime tasks for non-root users until you allocate
954 realtime bandwidth for them.
955 See Documentation/scheduler/sched-rt-group.txt for more information.
956 957endif #CGROUP_SCHED
958 959config BLK_CGROUP
960 bool "Block IO controller"
961 depends on BLOCK
962 default n
963 ---help---
964 Generic block IO controller cgroup interface. This is the common
965 cgroup interface which should be used by various IO controlling
966 policies.
967 968 Currently, CFQ IO scheduler uses it to recognize task groups and
969 control disk bandwidth allocation (proportional time slice allocation)
970 to such task groups. It is also used by bio throttling logic in
971 block layer to implement upper limit in IO rates on a device.
972 973 This option only enables generic Block IO controller infrastructure.
974 One needs to also enable actual IO controlling logic/policy. For
975 enabling proportional weight division of disk bandwidth in CFQ, set
976 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
977 CONFIG_BLK_DEV_THROTTLING=y.
978 979 See Documentation/cgroups/blkio-controller.txt for more information.
980 981config DEBUG_BLK_CGROUP
982 bool "Enable Block IO controller debugging"
983 depends on BLK_CGROUP
984 default n
985 ---help---
986 Enable some debugging help. Currently it exports additional stat
987 files in a cgroup which can be useful for debugging.
988 989endif # CGROUPS
990 991config CHECKPOINT_RESTORE
992 bool "Checkpoint/restore support" if EXPERT
993 default n
994 help
995 Enables additional kernel features in a sake of checkpoint/restore.
996 In particular it adds auxiliary prctl codes to setup process text,
997 data and heap segment sizes, and a few additional /proc filesystem
998 entries.
9991000 If unsure, say N here.

10011002menuconfig NAMESPACES
1003 bool "Namespaces support" if EXPERT
1004 default !EXPERT
1005 help
1006 Provides the way to make tasks work with different objects using
1007 the same id. For example same IPC id may refer to different objects
1008 or same user id or pid may refer to different tasks when used in
1009 different namespaces.
10101011if NAMESPACES
10121013config UTS_NS
1014 bool "UTS namespace"
1015 default y
1016 help
1017 In this namespace tasks see different info provided with the
1018 uname() system call
10191020config IPC_NS
1021 bool "IPC namespace"
1022 depends on (SYSVIPC || POSIX_MQUEUE)
1023 default y
1024 help
1025 In this namespace tasks work with IPC ids which correspond to
1026 different IPC objects in different namespaces.
10271028config USER_NS
1029 bool "User namespace (EXPERIMENTAL)"
1030 depends on EXPERIMENTAL
1031 depends on UIDGID_CONVERTED
1032 select UIDGID_STRICT_TYPE_CHECKS
10331034 default n
1035 help
1036 This allows containers, i.e. vservers, to use user namespaces
1037 to provide different user info for different servers.
1038 If unsure, say N.
10391040config PID_NS
1041 bool "PID Namespaces"
1042 default y
1043 help
1044 Support process id namespaces. This allows having multiple
1045 processes with the same pid as long as they are in different
1046 pid namespaces. This is a building block of containers.
10471048config NET_NS
1049 bool "Network namespace"
1050 depends on NET
1051 default y
1052 help
1053 Allow user space to create what appear to be multiple instances
1054 of the network stack.
10551056endif # NAMESPACES
10571058config UIDGID_CONVERTED
1059 # True if all of the selected software conmponents are known
1060 # to have uid_t and gid_t converted to kuid_t and kgid_t
1061 # where appropriate and are otherwise safe to use with
1062 # the user namespace.
1063 bool
1064 default y
10651066 # Networking
1067 depends on NET_9P = n
10681069 # Filesystems
1070 depends on 9P_FS = n
1071 depends on AFS_FS = n
1072 depends on CEPH_FS = n
1073 depends on CIFS = n
1074 depends on CODA_FS = n
1075 depends on GFS2_FS = n
1076 depends on NCP_FS = n
1077 depends on NFSD = n
1078 depends on NFS_FS = n
1079 depends on OCFS2_FS = n
1080 depends on XFS_FS = n
10811082config UIDGID_STRICT_TYPE_CHECKS
1083 bool "Require conversions between uid/gids and their internal representation"
1084 depends on UIDGID_CONVERTED
1085 default n
1086 help
1087 While the nececessary conversions are being added to all subsystems this option allows
1088 the code to continue to build for unconverted subsystems.
10891090 Say Y here if you want the strict type checking enabled
10911092config SCHED_AUTOGROUP
1093 bool "Automatic process group scheduling"
1094 select EVENTFD
1095 select CGROUPS
1096 select CGROUP_SCHED
1097 select FAIR_GROUP_SCHED
1098 help
1099 This option optimizes the scheduler for common desktop workloads by
1100 automatically creating and populating task groups. This separation
1101 of workloads isolates aggressive CPU burners (like build jobs) from
1102 desktop applications. Task group autogeneration is currently based
1103 upon task session.
11041105config MM_OWNER
1106 bool
11071108config SYSFS_DEPRECATED
1109 bool "Enable deprecated sysfs features to support old userspace tools"
1110 depends on SYSFS
1111 default n
1112 help
1113 This option adds code that switches the layout of the "block" class
1114 devices, to not show up in /sys/class/block/, but only in
1115 /sys/block/.
11161117 This switch is only active when the sysfs.deprecated=1 boot option is
1118 passed or the SYSFS_DEPRECATED_V2 option is set.
11191120 This option allows new kernels to run on old distributions and tools,
1121 which might get confused by /sys/class/block/. Since 2007/2008 all
1122 major distributions and tools handle this just fine.
11231124 Recent distributions and userspace tools after 2009/2010 depend on
1125 the existence of /sys/class/block/, and will not work with this
1126 option enabled.
11271128 Only if you are using a new kernel on an old distribution, you might
1129 need to say Y here.
11301131config SYSFS_DEPRECATED_V2
1132 bool "Enable deprecated sysfs features by default"
1133 default n
1134 depends on SYSFS
1135 depends on SYSFS_DEPRECATED
1136 help
1137 Enable deprecated sysfs by default.
11381139 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1140 option.
11411142 Only if you are using a new kernel on an old distribution, you might
1143 need to say Y here. Even then, odds are you would not need it
1144 enabled, you can always pass the boot option if absolutely necessary.
11451146config RELAY
1147 bool "Kernel->user space relay support (formerly relayfs)"
1148 help
1149 This option enables support for relay interface support in
1150 certain file systems (such as debugfs).
1151 It is designed to provide an efficient mechanism for tools and
1152 facilities to relay large amounts of data from kernel space to
1153 user space.
11541155 If unsure, say N.
11561157config BLK_DEV_INITRD
1158 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1159 depends on BROKEN || !FRV
1160 help
1161 The initial RAM filesystem is a ramfs which is loaded by the
1162 boot loader (loadlin or lilo) and that is mounted as root
1163 before the normal boot procedure. It is typically used to
1164 load modules needed to mount the "real" root file system,
1165 etc. See <file:Documentation/initrd.txt> for details.
11661167 If RAM disk support (BLK_DEV_RAM) is also included, this
1168 also enables initial RAM disk (initrd) support and adds
1169 15 Kbytes (more on some other architectures) to the kernel size.
11701171 If unsure say Y.
11721173if BLK_DEV_INITRD
11741175source "usr/Kconfig"
11761177endif
11781179config CC_OPTIMIZE_FOR_SIZE
1180 bool "Optimize for size"
1181 help
1182 Enabling this option will pass "-Os" instead of "-O2" to gcc
1183 resulting in a smaller kernel.
11841185 If unsure, say N.
11861187config SYSCTL
1188 bool
11891190config ANON_INODES
1191 bool
11921193menuconfig EXPERT
1194 bool "Configure standard kernel features (expert users)"
1195 # Unhide debug options, to make the on-by-default options visible
1196 select DEBUG_KERNEL
1197 help
1198 This option allows certain base kernel options and settings
1199 to be disabled or tweaked. This is for specialized
1200 environments which can tolerate a "non-standard" kernel.
1201 Only use this if you really know what you are doing.
12021203config HAVE_UID16
1204 bool
12051206config UID16
1207 bool "Enable 16-bit UID system calls" if EXPERT
1208 depends on HAVE_UID16
1209 default y
1210 help
1211 This enables the legacy 16-bit UID syscall wrappers.
12121213config SYSCTL_SYSCALL
1214 bool "Sysctl syscall support" if EXPERT
1215 depends on PROC_SYSCTL
1216 default n
1217 select SYSCTL
1218 ---help---
1219 sys_sysctl uses binary paths that have been found challenging
1220 to properly maintain and use. The interface in /proc/sys
1221 using paths with ascii names is now the primary path to this
1222 information.
12231224 Almost nothing using the binary sysctl interface so if you are
1225 trying to save some space it is probably safe to disable this,
1226 making your kernel marginally smaller.
12271228 If unsure say N here.
12291230config SYSCTL_EXCEPTION_TRACE
1231 bool
1232 help
1233 Enable support for /proc/sys/debug/exception-trace.
12341235config KALLSYMS
1236 bool "Load all symbols for debugging/ksymoops" if EXPERT
1237 default y
1238 help
1239 Say Y here to let the kernel print out symbolic crash information and
1240 symbolic stack backtraces. This increases the size of the kernel
1241 somewhat, as all symbols have to be loaded into the kernel image.
12421243config KALLSYMS_ALL
1244 bool "Include all symbols in kallsyms"
1245 depends on DEBUG_KERNEL && KALLSYMS
1246 help
1247 Normally kallsyms only contains the symbols of functions for nicer
1248 OOPS messages and backtraces (i.e., symbols from the text and inittext
1249 sections). This is sufficient for most cases. And only in very rare
1250 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1251 names of variables from the data sections, etc).
12521253 This option makes sure that all symbols are loaded into the kernel
1254 image (i.e., symbols from all sections) in cost of increased kernel
1255 size (depending on the kernel configuration, it may be 300KiB or
1256 something like this).
12571258 Say N unless you really need all symbols.
12591260config HOTPLUG
1261 def_bool y
12621263config PRINTK
1264 default y
1265 bool "Enable support for printk" if EXPERT
1266 help
1267 This option enables normal printk support. Removing it
1268 eliminates most of the message strings from the kernel image
1269 and makes the kernel more or less silent. As this makes it
1270 very difficult to diagnose system problems, saying N here is
1271 strongly discouraged.
12721273config BUG
1274 bool "BUG() support" if EXPERT
1275 default y
1276 help
1277 Disabling this option eliminates support for BUG and WARN, reducing
1278 the size of your kernel image and potentially quietly ignoring
1279 numerous fatal conditions. You should only consider disabling this
1280 option for embedded systems with no facilities for reporting errors.
1281 Just say Y.
12821283config ELF_CORE
1284 depends on COREDUMP
1285 default y
1286 bool "Enable ELF core dumps" if EXPERT
1287 help
1288 Enable support for generating core dumps. Disabling saves about 4k.
128912901291config PCSPKR_PLATFORM
1292 bool "Enable PC-Speaker support" if EXPERT
1293 depends on HAVE_PCSPKR_PLATFORM
1294 select I8253_LOCK
1295 default y
1296 help
1297 This option allows to disable the internal PC-Speaker
1298 support, saving some memory.
12991300config HAVE_PCSPKR_PLATFORM
1301 bool
13021303config BASE_FULL
1304 default y
1305 bool "Enable full-sized data structures for core" if EXPERT
1306 help
1307 Disabling this option reduces the size of miscellaneous core
1308 kernel data structures. This saves memory on small machines,
1309 but may reduce performance.
13101311config FUTEX
1312 bool "Enable futex support" if EXPERT
1313 default y
1314 select RT_MUTEXES
1315 help
1316 Disabling this option will cause the kernel to be built without
1317 support for "fast userspace mutexes". The resulting kernel may not
1318 run glibc-based applications correctly.
13191320config EPOLL
1321 bool "Enable eventpoll support" if EXPERT
1322 default y
1323 select ANON_INODES
1324 help
1325 Disabling this option will cause the kernel to be built without
1326 support for epoll family of system calls.
13271328config SIGNALFD
1329 bool "Enable signalfd() system call" if EXPERT
1330 select ANON_INODES
1331 default y
1332 help
1333 Enable the signalfd() system call that allows to receive signals
1334 on a file descriptor.
13351336 If unsure, say Y.
13371338config TIMERFD
1339 bool "Enable timerfd() system call" if EXPERT
1340 select ANON_INODES
1341 default y
1342 help
1343 Enable the timerfd() system call that allows to receive timer
1344 events on a file descriptor.
13451346 If unsure, say Y.
13471348config EVENTFD
1349 bool "Enable eventfd() system call" if EXPERT
1350 select ANON_INODES
1351 default y
1352 help
1353 Enable the eventfd() system call that allows to receive both
1354 kernel notification (ie. KAIO) or userspace notifications.
13551356 If unsure, say Y.
13571358config SHMEM
1359 bool "Use full shmem filesystem" if EXPERT
1360 default y
1361 depends on MMU
1362 help
1363 The shmem is an internal filesystem used to manage shared memory.
1364 It is backed by swap and manages resource limits. It is also exported
1365 to userspace as tmpfs if TMPFS is enabled. Disabling this
1366 option replaces shmem and tmpfs with the much simpler ramfs code,
1367 which may be appropriate on small systems without swap.
13681369config AIO
1370 bool "Enable AIO support" if EXPERT
1371 default y
1372 help
1373 This option enables POSIX asynchronous I/O which may by used
1374 by some high performance threaded applications. Disabling
1375 this option saves about 7k.
13761377config EMBEDDED
1378 bool "Embedded system"
1379 select EXPERT
1380 help
1381 This option should be enabled if compiling the kernel for
1382 an embedded system so certain expert options are available
1383 for configuration.
13841385config HAVE_PERF_EVENTS
1386 bool
1387 help
1388 See tools/perf/design.txt for details.
13891390config PERF_USE_VMALLOC
1391 bool
1392 help
1393 See tools/perf/design.txt for details
13941395menu "Kernel Performance Events And Counters"
13961397config PERF_EVENTS
1398 bool "Kernel performance events and counters"
1399 default y if PROFILING
1400 depends on HAVE_PERF_EVENTS
1401 select ANON_INODES
1402 select IRQ_WORK
1403 help
1404 Enable kernel support for various performance events provided
1405 by software and hardware.
14061407 Software events are supported either built-in or via the
1408 use of generic tracepoints.
14091410 Most modern CPUs support performance events via performance
1411 counter registers. These registers count the number of certain
1412 types of hw events: such as instructions executed, cachemisses
1413 suffered, or branches mis-predicted - without slowing down the
1414 kernel or applications. These registers can also trigger interrupts
1415 when a threshold number of events have passed - and can thus be
1416 used to profile the code that runs on that CPU.
14171418 The Linux Performance Event subsystem provides an abstraction of
1419 these software and hardware event capabilities, available via a
1420 system call and used by the "perf" utility in tools/perf/. It
1421 provides per task and per CPU counters, and it provides event
1422 capabilities on top of those.
14231424 Say Y if unsure.
14251426config DEBUG_PERF_USE_VMALLOC
1427 default n
1428 bool "Debug: use vmalloc to back perf mmap() buffers"
1429 depends on PERF_EVENTS && DEBUG_KERNEL
1430 select PERF_USE_VMALLOC
1431 help
1432 Use vmalloc memory to back perf mmap() buffers.
14331434 Mostly useful for debugging the vmalloc code on platforms
1435 that don't require it.
14361437 Say N if unsure.
14381439endmenu
14401441config VM_EVENT_COUNTERS
1442 default y
1443 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1444 help
1445 VM event counters are needed for event counts to be shown.
1446 This option allows the disabling of the VM event counters
1447 on EXPERT systems. /proc/vmstat will only show page counts
1448 if VM event counters are disabled.
14491450config PCI_QUIRKS
1451 default y
1452 bool "Enable PCI quirk workarounds" if EXPERT
1453 depends on PCI
1454 help
1455 This enables workarounds for various PCI chipset
1456 bugs/quirks. Disable this only if your target machine is
1457 unaffected by PCI quirks.
14581459config SLUB_DEBUG
1460 default y
1461 bool "Enable SLUB debugging support" if EXPERT
1462 depends on SLUB && SYSFS
1463 help
1464 SLUB has extensive debug support features. Disabling these can
1465 result in significant savings in code size. This also disables
1466 SLUB sysfs support. /sys/slab will not exist and there will be
1467 no support for cache validation etc.
14681469config COMPAT_BRK
1470 bool "Disable heap randomization"
1471 default y
1472 help
1473 Randomizing heap placement makes heap exploits harder, but it
1474 also breaks ancient binaries (including anything libc5 based).
1475 This option changes the bootup default to heap randomization
1476 disabled, and can be overridden at runtime by setting
1477 /proc/sys/kernel/randomize_va_space to 2.
14781479 On non-ancient distros (post-2000 ones) N is usually a safe choice.
14801481choice
1482 prompt "Choose SLAB allocator"
1483 default SLUB
1484 help
1485 This option allows to select a slab allocator.
14861487config SLAB
1488 bool "SLAB"
1489 help
1490 The regular slab allocator that is established and known to work
1491 well in all environments. It organizes cache hot objects in
1492 per cpu and per node queues.
14931494config SLUB
1495 bool "SLUB (Unqueued Allocator)"
1496 help
1497 SLUB is a slab allocator that minimizes cache line usage
1498 instead of managing queues of cached objects (SLAB approach).
1499 Per cpu caching is realized using slabs of objects instead
1500 of queues of objects. SLUB can use memory efficiently
1501 and has enhanced diagnostics. SLUB is the default choice for
1502 a slab allocator.
15031504config SLOB
1505 depends on EXPERT
1506 bool "SLOB (Simple Allocator)"
1507 help
1508 SLOB replaces the stock allocator with a drastically simpler
1509 allocator. SLOB is generally more space efficient but
1510 does not perform as well on large systems.
15111512endchoice
15131514config MMAP_ALLOW_UNINITIALIZED
1515 bool "Allow mmapped anonymous memory to be uninitialized"
1516 depends on EXPERT && !MMU
1517 default n
1518 help
1519 Normally, and according to the Linux spec, anonymous memory obtained
1520 from mmap() has it's contents cleared before it is passed to
1521 userspace. Enabling this config option allows you to request that
1522 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1523 providing a huge performance boost. If this option is not enabled,
1524 then the flag will be ignored.
15251526 This is taken advantage of by uClibc's malloc(), and also by
1527 ELF-FDPIC binfmt's brk and stack allocator.
15281529 Because of the obvious security issues, this option should only be
1530 enabled on embedded devices where you control what is run in
1531 userspace. Since that isn't generally a problem on no-MMU systems,
1532 it is normally safe to say Y here.
15331534 See Documentation/nommu-mmap.txt for more information.
15351536config PROFILING
1537 bool "Profiling support"
1538 help
1539 Say Y here to enable the extended profiling support mechanisms used
1540 by profilers such as OProfile.
15411542#
1543# Place an empty function call at each tracepoint site. Can be
1544# dynamically changed for a probe function.
1545#
1546config TRACEPOINTS
1547 bool
15481549source "arch/Kconfig"
15501551endmenu # General setup
15521553config HAVE_GENERIC_DMA_COHERENT
1554 bool
1555 default n
15561557config SLABINFO
1558 bool
1559 depends on PROC_FS
1560 depends on SLAB || SLUB_DEBUG
1561 default y
15621563config RT_MUTEXES
1564 boolean
15651566config BASE_SMALL
1567 int
1568 default 0 if BASE_FULL
1569 default 1 if !BASE_FULL
15701571menuconfig MODULES
1572 bool "Enable loadable module support"
1573 help
1574 Kernel modules are small pieces of compiled code which can
1575 be inserted in the running kernel, rather than being
1576 permanently built into the kernel. You use the "modprobe"
1577 tool to add (and sometimes remove) them. If you say Y here,
1578 many parts of the kernel can be built as modules (by
1579 answering M instead of Y where indicated): this is most
1580 useful for infrequently used options which are not required
1581 for booting. For more information, see the man pages for
1582 modprobe, lsmod, modinfo, insmod and rmmod.
15831584 If you say Y here, you will need to run "make
1585 modules_install" to put the modules under /lib/modules/
1586 where modprobe can find them (you may need to be root to do
1587 this).
15881589 If unsure, say Y.
15901591if MODULES
15921593config MODULE_FORCE_LOAD
1594 bool "Forced module loading"
1595 default n
1596 help
1597 Allow loading of modules without version information (ie. modprobe
1598 --force). Forced module loading sets the 'F' (forced) taint flag and
1599 is usually a really bad idea.
16001601config MODULE_UNLOAD
1602 bool "Module unloading"
1603 help
1604 Without this option you will not be able to unload any
1605 modules (note that some modules may not be unloadable
1606 anyway), which makes your kernel smaller, faster
1607 and simpler. If unsure, say Y.
16081609config MODULE_FORCE_UNLOAD
1610 bool "Forced module unloading"
1611 depends on MODULE_UNLOAD && EXPERIMENTAL
1612 help
1613 This option allows you to force a module to unload, even if the
1614 kernel believes it is unsafe: the kernel will remove the module
1615 without waiting for anyone to stop using it (using the -f option to
1616 rmmod). This is mainly for kernel developers and desperate users.
1617 If unsure, say N.
16181619config MODVERSIONS
1620 bool "Module versioning support"
1621 help
1622 Usually, you have to use modules compiled with your kernel.
1623 Saying Y here makes it sometimes possible to use modules
1624 compiled for different kernels, by adding enough information
1625 to the modules to (hopefully) spot any changes which would
1626 make them incompatible with the kernel you are running. If
1627 unsure, say N.
16281629config MODULE_SRCVERSION_ALL
1630 bool "Source checksum for all modules"
1631 help
1632 Modules which contain a MODULE_VERSION get an extra "srcversion"
1633 field inserted into their modinfo section, which contains a
1634 sum of the source files which made it. This helps maintainers
1635 see exactly which source was used to build a module (since
1636 others sometimes change the module source without updating
1637 the version). With this option, such a "srcversion" field
1638 will be created for all modules. If unsure, say N.
16391640config MODULE_SIG
1641 bool "Module signature verification"
1642 depends on MODULES
1643 select KEYS
1644 select CRYPTO
1645 select ASYMMETRIC_KEY_TYPE
1646 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1647 select PUBLIC_KEY_ALGO_RSA
1648 select ASN1
1649 select OID_REGISTRY
1650 select X509_CERTIFICATE_PARSER
1651 help
1652 Check modules for valid signatures upon load: the signature
1653 is simply appended to the module. For more information see
1654 Documentation/module-signing.txt.
16551656 !!!WARNING!!! If you enable this option, you MUST make sure that the
1657 module DOES NOT get stripped after being signed. This includes the
1658 debuginfo strip done by some packagers (such as rpmbuild) and
1659 inclusion into an initramfs that wants the module size reduced.
16601661config MODULE_SIG_FORCE
1662 bool "Require modules to be validly signed"
1663 depends on MODULE_SIG
1664 help
1665 Reject unsigned modules or signed modules for which we don't have a
1666 key. Without this, such modules will simply taint the kernel.
16671668choice
1669 prompt "Which hash algorithm should modules be signed with?"
1670 depends on MODULE_SIG
1671 help
1672 This determines which sort of hashing algorithm will be used during
1673 signature generation. This algorithm _must_ be built into the kernel
1674 directly so that signature verification can take place. It is not
1675 possible to load a signed module containing the algorithm to check
1676 the signature on that module.
16771678config MODULE_SIG_SHA1
1679 bool "Sign modules with SHA-1"
1680 select CRYPTO_SHA1
16811682config MODULE_SIG_SHA224
1683 bool "Sign modules with SHA-224"
1684 select CRYPTO_SHA256
16851686config MODULE_SIG_SHA256
1687 bool "Sign modules with SHA-256"
1688 select CRYPTO_SHA256
16891690config MODULE_SIG_SHA384
1691 bool "Sign modules with SHA-384"
1692 select CRYPTO_SHA512
16931694config MODULE_SIG_SHA512
1695 bool "Sign modules with SHA-512"
1696 select CRYPTO_SHA512
16971698endchoice
16991700endif # MODULES
17011702config INIT_ALL_POSSIBLE
1703 bool
1704 help
1705 Back when each arch used to define their own cpu_online_mask and
1706 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1707 with all 1s, and others with all 0s. When they were centralised,
1708 it was better to provide this option than to break all the archs
1709 and have several arch maintainers pursuing me down dark alleys.
17101711config STOP_MACHINE
1712 bool
1713 default y
1714 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1715 help
1716 Need stop_machine() primitive.
17171718source "block/Kconfig"
17191720config PREEMPT_NOTIFIERS
1721 bool
17221723config PADATA
1724 depends on SMP
1725 bool
17261727# Can be selected by architectures with broken toolchains
1728# that get confused by correct const<->read_only section
1729# mappings
1730config BROKEN_RODATA
1731 bool
17321733config ASN1
1734 tristate
1735 help
1736 Build a simple ASN.1 grammar compiler that produces a bytecode output
1737 that can be interpreted by the ASN.1 stream decoder and used to
1738 inform it as to what tags are to be expected in a stream and what
1739 functions to call on what tags.
17401741source "kernel/Kconfig.locks"
1742